Life-Threatening Diffuse Alveolar Hemorrhage and Graft Failure in Atypical Hemolytic Uremic Syndrome with C3 Gene Mutation following Kidney Transplant.

Introduction: Atypical hemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy (TMA) disease entity primarily attributed to genetic or acquired abnormalities in the alternative complement pathway. TMA can manifest in kidney transplant (KT) recipients owing to various factors, resulting in diverse clinical presentations. Given its adverse effects on allograft function and patient prognosis, genetic diagnostic approaches for aHUS are essential. Although rarely associated with diffuse alveolar hemorrhage, only a few mild cases have been reported to date. In this report, we present a case of the patient who experienced recurrent and life-threatening diffuse alveolar hemorrhage shortly after KT accompanied by graft failure.

Case presentation: An 18-year-old girl who underwent deceased donor KT developed recurrent diffuse alveolar hemorrhage with acute kidney injury, leading to graft failure. Microangiopathic hemolytic anemia, thrombocytopenia, and schistocytes in blood smears suggested the presence of TMA. The patient underwent therapeutic plasma exchange, and clinical condition improved during the procedure. Genetic testing confirmed a heterozygous c.1273C>T mutation in C3 gene, leading to the diagnosis of aHUS. However, after discontinuing the plasma exchange, the patient experienced seizures, recurrent pulmonary hemorrhage, and oliguria with recurring TMA features. The patient subsequently underwent eculizumab treatment, which resulted in complete remission, although hemodialysis was continued after graft nephrectomy.

Conclusion: In patients presenting with unexplained pulmonary hemorrhage and kidney injury following KT, genetic aHUS should be considered as a potential differential diagnosis for TMA.